1. Field of the Invention
The present invention relates to a disk drive apparatus, which is typically a hard disk drive.
2. Background Art
A hard disk drive (hereinafter, to be referred to as the HDD), which is the most popular storage means for computer data, is structured so that a single or a plurality of magnetic disks are disposed on one and the same axis and driven rotationally by a spindle motor therein. A head provided so as to face each magnetic disk reads/writes data from/on the disk. The head is driven by an actuator, usually by a voice coil motor (hereinafter, to be described as the VCM). The magnetic disk, the head, and the actuator are all housed in housing referred to as a disk enclosure. The disk enclosure is configured by a thin-box-like base made of an aluminum alloy and a top cover used to seal the opening of the base. Improvement of the storage capacity per magnetic disk and improvement of the speed for reading/writing data from/on the magnetic disk have been main technical issues for improvement of the HDD.
The latter issue, that is, improvement of the speed for reading/writing data, can be achieved by reducing the seek time of the head that moves to a target track on the subject disk. This seek time can also be improved by improving the performance of the VCM, since the VCM drives the head as described above. And, in order to improve the performance of the VCM, it is only required to make the magnetic power of the permanent magnet of the VCM more stronger or increase the thickness of the permanent magnet, thereby increasing the magnetic field to be applied to the voice coil. The improvement of the magnetic power of the permanent magnet, however, has already reached its technical limit. In addition, the thickness of the permanent magnet cannot be increased any longer in such the HDD whose compaction is demanded more and more.
Furthermore, the speed for reading/writing data can also be improved by speeding up the rotation of the magnetic disk. As the rotation of the magnetic disk is speeded up such way, however, a problem arises from the sound or vibration properties of the subject HDD.
3. Problems to be Solved by the Invention
Conventionally, a damper has been stuck on the subject HDD so as to repress the HDD vibration. The damper is made of, for example, stainless steel. FIG. 9 shows an example of such a damper having been used conventionally. The damper 50 shown in FIG. 9 is formed by punching a flat plate into a predetermined shape. In this case, therefore, the HDD design parameters to be changed freely are the external dimension and the thickness of the HDD. And, the external dimension is limited by the size of the HDD. For example, the external dimension is just permitted to have such an additional portion as the damper 51 shown in FIG. 10 at part thereof. An increase of the wall thickness of the HDD might also cause the life of the punching mold for punching the damper to be reduced and such an increase of the wall-thickness is limited by the size of the HDD.
The conventional HDD includes two problems to arise from sound or vibration.
One is existence of a sound frequency peak to be generated by the rotation of the spindle motor for driving the HDD. Although a damper is formed so as to reduce this sound frequency, the sound frequency is often amplified when the resonant frequency of the damper matches with the HDD sound frequency band in which a sound frequency peak is generated by the rotation of the spindle motor (hereinafter, to be referred to as an HDD sound peak frequency band). Especially, as the rotation speed of the spindle motor is increased, this sound frequency amplification becomes remarkable. In order to avoid this problem, therefore, much care must be taken for shifting the resonant frequency of the damper from the HDD sound peak frequency band when the damper 50 or 51 is formed in the HDD whose rotation speed is fast, concretely over 10,000 rpm. In spite of this, such the consideration for the damper 50 or 51 is also limited due to the HDD design.
The above HDD vibration problem occurs as a reaction to the seek operation of the actuator. This vibration is referred to as a rotational vibration (R.V.). In order to improve the HDD properties to reduce the R.V., therefore, a well-known method has been proposed so as to increase the mass of the damper 50/51. In case the mass of the damper 50/51 is increased, however, the damper must also be increased in thickness or a plurality of dampers must be bonded together. The conventional method has not taken such the measure enough due to the limitation by the HDD design as described above.
There is also a well-known method for disposing a member that increases the mass at an outer periphery area of the HDD so as to increase the moment, which functions as a resistance to the above R.V. And, an attempt has been made to fix the member (mass) by screws at an outer periphery area of the HDD. In case the member (mass) is fixed by screws such way, an additional work must be added to the manufacturing process, thereby the manufacturing cost is increased. Under such circumstances, it is an object of the present invention to provide a damper that solves the above conventional problems, thereby providing a disk drive apparatus excellent in sound or vibration properties.
The inventor of the present invention has examined a method for increasing the wall thickness of a damper partially while examination has been done conventionally so as to change the shape of the damper whose wall thickness is premised to be fixed. As a result, the inventor has found that it is easy to shift the resonant frequency of the damper from the HDD sound peak frequency band. In other words, it is easy to avoid the matching between the resonant frequency of the damper and the HDD sound peak frequency band in case the wall thickness of the damper is increased partially. On the contrary, the inventor has also found that it is not easy to shift the resonant frequency of the damper from the peak band even when the wall thickness of the damper is increased in case the damper is fixed in thickness.
The present invention is based on such the knowledge and the damper of the present invention is attached to the subject disk drive apparatus and enabled to repress the HDD vibration. The damper comprises a flat portion having a jointing surface onto the disk drive apparatus and a wall-thickness portion that is thicker than the flat portion. The damper of the present invention has a three-dimensional shape while the conventional flat damper whose thickness is in uniform has a two-dimensional shape. Consequently, the damper can be varied more freely in shape, thereby it is possible to adjust the resonant frequency of the damper more freely. It is thus possible to shift the resonant frequency of the damper from the HDD sound peak frequency band more easily.
Basically, the damper of the present invention enables the wall-thickness portion to be formed at any position thereon. Preferably, however, it should be formed at an outer periphery area of the flat portion. For example, in case the damper of the present invention is to be attached to an HDD, a space for housing the wall-thickness portion will have to be provided on the housing of the HDD. This is because it would be easy to secure such a space at an outer periphery area of the HDD housing. As for the R.V. problem, the wall-thickness portion should preferably be formed at such an outer periphery area. And, when the mass is the same, disposing the wall-thickness portion at such an periphery area makes it possible to get a larger moment, which is effective for reducing the R.V.
The damper of the present invention also enables the wall-thickness portion as described above to be formed at a plurality of places thereon. This is because there is a case preferred to shift the resonant frequency of the damper from the HDD sound peak frequency band. This method is also effective when it is difficult to form a wall-thickness portion that can satisfy the thickness requirement by itself.
While the damper of the present invention is characterized by a wall-thickness portion formed thereon as described above, this wall-thickness portion means a portion of the damper where the mass is increased locally. Therefore, the present invention can also provide a flat damper attached to a disk drive apparatus and enabled to repress the vibration of the apparatus. The damper may also include a flat portion having a jointing portion onto the disk drive apparatus; a mass-increased portion disposed at an outer periphery area of the flat portion and having larger mass per unit area than the flat portion.
The damper of the present invention disposes its mass-increased portion at an outer periphery area of the flat portion. This mass-increased portion makes it easy to shift the damper resonant frequency from the HDD sound frequency peak band. And, because the mass-increased portion is disposed at an outer periphery area of the flat portion, the damper can be attached to the target HDD in a preferred form as described above. And, because the mass-increased portion is disposed at an outer periphery area of the flat portion, the damper can reduce the R.V. significantly. Concretely, the damper of the present invention can obtain two types of effects; the damper resonant frequency can be easily shifted from the HDD sound peak frequency band and the properties of the damper effective to reduce the R.V. can be improved.
In case it is premised that dampers are made of the same material, the mass-increased portion can be formed only by increasing that portion on the damper of the present invention. In case dampers are to be made of two or more materials, however, the mass-increased portion can be formed by disposing a material whose specific gravity is larger than other portions at an outer periphery area of the damper. In this case, it is possible to uniform the wall thickness of the damper.
The present invention also provides a disk drive apparatus to which the above-described damper is attached. Concretely, the disk drive apparatus of the present invention comprises a disk-like medium driven rotationally around a rotation axis and enabled to store data thereon; an actuator having a head for reading/writing data from/on the disk-like medium and being rotated around the rotation axis; housing for housing the disk-like medium and the actuator; and a damper formed at an outer surface of the housing and having a plurality of thick portions.
The disk drive apparatus of the present invention can shift the damper resonant frequency from the HDD sound peak frequency band easily, since the damper has a plurality of portions, each of which differs in thickness from others.
In the disk drive apparatus of the present invention, the damper should preferably be configured by a wall-thickness portion formed at an outer periphery area thereof and a flat portion except for the wall-thickness portion as described above.
Furthermore, in the disk drive apparatus of the present invention, the damper should preferably be formed so that the flat portion is stuck on the housing and the wall-thickness portion is not in contact with the housing. And, the means for attaching the damper to the housing may be mechanical jointing means, which is screws. However, in case the housing and the damper are configured with materials whose linear expansion coefficients are different from each other, the housing might be deformed due to a temperature stress caused by such the difference between those linear expansion coefficients. On the contrary, in case an adhesive agent or double-coated tape is used to stick the damper on the housing, it is expected that the adhesive agent or double-coated tape can function as a cushion member for absorbing such the temperature stress. Consequently, the sticking method is favorable as the jointing method. In this case, because the double-coated tape uses an adhesive agent, the sticking by such the double-coated tape may be considered to be sticking by an adhesive agent in the broad sense. And, separating the wall-thickness portion from the housing is to enable the wall-thickness portion to vibrate and make the vibration repress the vibration of the HDD enough. Employment of such vibration repressing structure employed for a disk drive apparatus is a novelty achieved by the present invention.
Furthermore, the wall-thickness portion in the disk drive apparatus of the present invention should preferably be formed at a plurality of places in the circumferential direction of the rotation axis of the actuator. In case the wall-thickness portion is assumed as the mass for repressing the R.V., the mass should be distributed at a plurality of places rather than it is concentrated at a place. And, because the R.V. is generated by a seek operation, that is, the rotation of the actuator, such a plurality of the wall-thickness portions formed in the circumferential direction of the rotation axis function effectively as resistance to the R.V.
The present invention also provides a disk drive apparatus comprising a disk-like medium driven rotationally around a rotation axis and enabled to store data thereon; an actuator having a head for reading/writing data from/on the disk-like medium and being driven around the rotation axis; housing for housing the disk-like medium and the actuator; and a damper formed at an outer surface of the housing so as to increase the mass more and more gradually towards the outer periphery area.
This disk drive apparatus, because it has a damper whose mass is increased more and more gradually towards the periphery area such way, can shift the damper resonance frequency from the HDD sound peak frequency band easily. And, because the mass is increased more and more gradually towards the outer periphery area, the properties of the disk drive apparatus are improved effectively so as to reduce the R.V.
The disk drive apparatus of the present invention can apply to an HDD. Consequently, the present invention can also provide a hard disk drive comprising a disk-like medium for storing data magnetically; a spindle motor for driving the disk-like medium rotationally; a rotary actuator having a magnetic head for writing/reading data on/from the disk-like medium and being enabled to seek the head to the disk-like medium and rotated around a pivot; a disk enclosure for housing the disk-like medium, the spindle motor, and the rotary actuator and being configured by a box-like base having an opening and a cover used to seal the opening; and a damper having a wall-thickness portion disposed at the bottom of the base and formed so as to become more thicker and thicker gradually towards the outer periphery area.
The hard disk drive of the present invention disables the damper to have a resonant frequency in the HDD sound peak frequency band to be generated by the rotation of the spindle motor. Consequently, the sound properties are not degraded even in a hard disk drive that has one or more disks driven fast.
The base in the hard disk drive of the present invention forms a housing space for housing the wall-thickness portion of the damper at an outer periphery portion where the disk-like medium does not exist and the wall-thickness portion of the damper can be housed in the housing space so as to vibrate. And, because the wall-thickness portion of the damper is never exposed to the outside of the hard disk drive and enabled to vibrate such way, the damper can repress the vibration of the hard disk drive with its vibration. In this case, in order to enable the wall-thickness portion to vibrate, it is just required to hold the wall-thickness portion in the housing space with a predetermined gap from the base.
The damper in the hard disk drive of the present invention should preferably be formed with a material whose specific gravity is larger than that of the material of the base. This is to make the damper repress the vibration of the hard disk drive more effectively.
When the wall-thickness portion of the damper is housed in the housing space so as to be enabled to vibrate there as described above, the wall-thickness portion functions as a so-called mass damper, thereby it can reduce the R.V. effectively. Consequently, the present invention comes to provide a hard disk drive comprising a disk-like medium for storing data magnetically; a spindle motor for driving the disk-like medium rotationally; a rotary actuator having a head for storing/reproducing data on/from the disk-like medium, seeking the head to the disk-like medium, and being rotated around a pivot; a disk enclosure for housing the disk-like medium, the spindle motor; and the rotary actuator, and being configured by a box-like base having an opening and a cover used to seal the opening; and a mass damper disposed with a predetermined gap from the base.